Proteins separated by electrophoresis in a gel or following transfer to a membrane have traditionally been detected using visible organic dyes. The detection limit using chromogenic dyes such as Coomassie G250 or Coomassie R250 is generally in the range of 1 ng to 10 ng. Fluorescent methods of protein detection offer good sensitivities and multiplexing capabilities. For example, they allow detection of a post-translationally modified protein such as a glycoprotein with a specific stain in combination with a total protein stain. Such fluorescent dyes and their methods of use in protein detection and quantitation are desirable.